This invention relates to fluid pressure and mechanically actuated percussion-ignitable primers.
Fluid pressure actuated primers have been used to provide sequential actuation of aircraft personnel escape systems. In these sequential actuation devices, fluid pressure ducted from the first actuation enters a chamber and pressurizes a shear pin supported piston breaking the shear pin driving a firing pin on the piston into a conventional primer, initiating the second sequence or pyrotechnic action. These units require O-ring seals around the piston and are limited in shelf life by the aging characteristics of the O-ring material.
Base fuzes for projectiles have long used fluid pressure of the propellant gas ducted through a port in the projectile base to initiate a primer or initiate a pyromechanical action. In these applications sealing is of the utmost importance to prevent hot propellant gas from entering the fuze explosive train and causing premature functioning in the gun or launcher.
Many aircraft and aerospace ordnance components are initiated by electric primers. While the use of electric initiation has generally proven satisfactory, difficulties have been encountered with premature ignition by stray electrical energy. As a result of these problems alternate forms of initiation such as LASER, fluidic and MDF (Mild Detonating Fuse) are sometimes specified. Automotive air bag crash safety systems using an electric primer initiated by an electric signal from a bumper mounted impact sensor present installation and servicing hazards due to the electrical test instrumentation and electric fields found in the automobile. Fluid pressure initiated air bags have been tested but limitations in available fluid pressure sensitive primers have restricted widespread application.